# Atomic Structure Atomic Structure - PowerPoint

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```					Atomic Structure

   Atoms are made of three subatomic particles.
   Those subatomic particles are called the
protons, neutrons and electrons.
   The center of the atom is called the nucleus.
   The electrons orbit the atom in distinct energy
levels
Now, let’s see what you know about the
subatomic particles. Which subatomic
particle has no charge and a mass of 1
a.m.u.?
1.   proton
25%   25%   25%   25%
2.   neutron
3.   valance
4.   electron

1     2     3     4
Which subatomic particle has a
positive charge and a mass of 1 a.m.u.?
25%   25%   25%   25%
1.   proton
2.   neutron
3.   valance
4.   electron

1     2     3     4
Which subatomic particle has a -1
charge and a mass of about 0 ?

1.   proton
25%   25%   25%   25%
2.   neutron
3.   valance
4.   electron

1     2     3     4
What is the term for electrons in the
outermost energy level?
25%   25%   25%   25%

1.    proton
2.    neutron
3.    valance
4.    electron

1     2     3     4
History of the Atom
460 BC   Democritus develops the idea of atoms

Democritus pounded up
materials in his mortar
and pestle until
reduced to smaller
and smaller particles,
which he called
ATOMA (Greek for
indivisible)
During that time, the most famous/popular
thinker was Aristotle. Aristotle believed
that all substances were made up of
combinations of Air, Earth, Fire and
Water. Since Aristotle was more popular
than Democritus, the idea of the four
elements was used for almost another 2000
years ! And the atoma was ignored!
1808   John Dalton

Dalton suggested
that all matter was
spheres that
bounce off of each
other with perfect
elasticity. He called
them ATOMS.
1808   John Dalton

Dalton suggested
that all matter was
spheres that
bounce off of each
other with perfect
elasticity. He called
them ATOMS.
J. J. Thompson
1898   Joseph J. Thompson
Thompson was an
English physicist
who found that
atoms could
sometimes eject a
far smaller
negative particle
which he called an
ELECTRON.
1904

Six years later, J J Thompson develops
the idea that an atom was made up of
electrons scattered unevenly within a
sphere, surrounded by a soup of
positive charge to balance the charge
of the atom. This description is known
as the PLUM PUDDING MODEL.
1910   Ernest Rutherford
Rutherford is famous for his
gold foil experiment. Gold is
extremely ductile, meaning
it can be stretched
extremely thin. His research
group fired helium nuclei at
a piece of gold foil only a
few atoms thick. Most of the
positively charge nuclei
passed through. Many were
unexpectedly deflected, and
a few bounced straight
back.
Rutherford’s gold foil experiment
the group to propose a
central, positively
charged nucleus. The
nucleus was
surrounded by the
negatively charged
electrons, held in place
by electrical attraction.
In his model, the
electrons were
randomly placed.
1913   Niels Bohr

A student of Rutherford’s,
Bohr suggested that
the electrons moved in
orbits like planets
circling the sun. And,
he proposed, each orbit
could only contain a set
number of electrons.
Bohr Model of Helium

Notice the four balls at the
center of the atom –
two positively charged
protons (red) and two
neutral neutrons
(green). The much
smaller negatively
charged electrons orbit
the nucleus at a single
energy level.
The Bohr Model of Nitrogen

How can one tell this is a
model of nitrogen?
Which element is represented by this Bohr
model?

25%   25%   25%   25%

1.   hydrogen
2.   lithium
3.   carbon
4.   neon
1     2     3     4
Which element is represented by this Bohr
model?

25%   25%   25%   25%

1.   hydrogen
2.   lithium
3.   carbon
4.   neon
1     2     3     4
Both of these electron orbitals are full.
The first shell can hold only two electrons.
The second energy level can hold eight.
Atomic Structure
Subatomic        Charge         Mass
particle

Proton            +1          1 a.m.u.

Neutron        No charge      1 a.m.u.

The element symbol can include the atomic
number (red) and the atomic mass (blue).
The atomic mass is equal to the number of
protons plus the number of neutrons.

4
2   He
Atomic Structure

   First energy level      →       2 electrons

   Second energy level             →      8 electrons

   Third energy level       →      8 electrons*

* The third energy level actually holds 18, but the level fills
with 8 first.
Atomic Structure

Two common ways to represent the atomic
structure of an element or compound:

Electron configuration

Bohr model
Electron Configuration

Nitrogen has 7 electrons, so where will they be?
The inner orbital fills first, so 2 electrons go
there. That leaves 5 to go in the second.

So the electron configuration of nitrogen can be
written:
14
7   N
2,5
What element has the electron
configuration 2,4 ?
25%   25%   25%   25%

1.   hydrogen
2.   carbon
3.   neon
4.   silicon

1     2     3     4
What element has the electron
configuration 2,8 ?
25%   25%   25%   25%

1.   hydrogen
2.   carbon
3.   neon
4.   silicon

1     2     3     4
What element has the electron
configuration 2,8,4 ?
25%   25%   25%   25%

1.   hydrogen
2.   carbon
3.   neon
4.   silicon

1     2     3     4
What element is represented by this Bohr
model?

25%   25%   25%   25%

1.   hydrogen
2.   carbon
3.   neon
4.   silicon
1      2     3      4
Summary

   The atomic number of an atom = number of
protons in the nucleus
   The atomic mass of an atom = number of
protons + number of neutrons (in the
nucleus)
   The number of protons = number of electrons
   Electrons orbit the nucleus in energy levels
   Each energy level can only hold a set number
of electrons
Let’s see what you remember. Who is
credited with first proposing an atom?
17%   17%   17%   17%   17%   17%

1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

1     2      3     4     5     6
Who is credited with first proposing that
electrons are in fixed energy levels?
17%   17%   17%   17%   17%   17%

1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

1     2      3     4     5     6
Who is credited with plum pudding model of
the atom?
17%   17%   17%   17%   17%   17%

1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

1     2      3     4     5     6
Who is credited with the center of an atom
has a positively charged center with his gold
foil experiment?
17%   17%   17%   17%   17%   17%
1.   Aristotle
2.   Democritus
3.   John Dalton
4.   J.J. Thompson
5.   Ernest Rutherford
6.   Neils Bohr

1     2      3     4     5     6
What does the blue “4” represent in the
expression?
4
2   He
25%   25%   25%   25%

1.   Color of the atom
2.   Number of neutrons
3.   Atomic number
4.   Atomic mass

1      2     3     4
What does the red “2” represent in the
expression?
4
2   He
25%   25%   25%   25%

1.   Color of the atom
2.   Number of neutrons
3.   Atomic number
4.   Atomic mass

1      2     3     4
Which subatomic particle has a mass
of 1 a.m.u. and no charge?
25%   25%   25%   25%

1.   proton
2.   neutron
3.   orbital
4.   electron

1     2     3     4
Which subatomic particle has almost
no mass and a charge of - 1?
25%   25%   25%   25%

1.   proton
2.   neutron
3.   orbital
4.   electron

1     2     3     4
Which subatomic particle has a mass
of 1 a.m.u. and a charge of + 1?
25%   25%   25%   25%

1.   proton
2.   neutron
3.   orbital
4.   electron

1     2     3     4
In which part of an atom are the
protons found?
25%   25%   25%   25%

1.   nucleus
2.   energy levels
3.   orbitals
4.   electron shells

1      2     3     4
In which part of an atom are the
neutrons found?
25%   25%   25%   25%

1.   nucleus
2.   energy levels
3.   orbitals
4.   electron shells

1      2     3     4
How many electrons can the first
energy level hold?
25%   25%   25%   25%

1.   one
2.   two
3.   six
4.   eight

1     2     3     4
How many electrons can the second
energy level hold?
25%   25%   25%   25%

1.   one
2.   two
3.   six
4.   eight

1     2     3     4
What element is represented by the
following Bohr model?

25%   25%   25%    25%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
1     2       3    4
What element is represented by the
electron configuration 2,4?
17%   17%   17%   17%   17%   17%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
5.   sililcon
6.   calcium

1     2      3     4     5     6
What element is represented by the
electron configuration 2,6?
17%   17%   17%   17%   17%   17%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
5.   sililcon
6.   calcium

1     2      3     4     5     6
What element is represented by the
electron configuration 2,8,8,2?
17%   17%   17%   17%   17%   17%

1.   hydrogen
2.   helium
3.   carbon
4.   oxygen
5.   sililcon
6.   calcium

1     2      3     4     5     6
GOOD JOB

Thanks for participating.

Credit goes to S. Morris for slide information.

```
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